Delocalized cationic azo dyes containing a thiazole moiety

Several new delocalized cationic azo dyes incorporating a bathochromic thiazole moiety have been prepared in moderate to good yields. The synthesis involved the Knoevenagel condensation of an intermediate azo compound, bearing a terminal formyl group, with methylenic bases generated in situ from benzoazolium and quinolinium salts. All dyes display strong absorption around 700 nm and have shown negative solvatochromic behaviour.     

Synthesis,characterization, and dyeing performance of some azo thienopyridine and thienopyrimidine dyes based on wool and nylon

A string of novel heterocyclic mono azo dyes were synthesized and their utilization in dyeing different fabrics as wool and nylon were discussed. Thienopyridine azo dyes 4 and 6 were prepared by reaction of chloro acetamidederivative 2 with diamino compounds to yield 3 and 5 , followed by reaction with NaNO₂/HCl and coupling with nucleophilic reagent. One-pot reaction of chloro acetamide 2 with ammonium thiocyanat in solvent ethanol gave the unexpected thienopyrimidine derivative 7 , which contain two active sites, the former is primary amine that was able to form diazonium salt that coupled with N,N-dimethylaniline, resorcinol, and/or self-coupling to afford the azo dyes 8-10 , and the latter is active methylene group that underwent coupling with different diazonium salts to give the azo thienopyrimidine derivative dye 11-15 . The dyeing performance of these azo dyes had been investigated in terms of their dyeing behavior and fastness properties on different fabrics. Results showed that the color strength (K/S) values, as well as, washing, rubbing, and resistance to acid, alkali and light showed high efficiency of these heterocyclic mono azo dyes to dye wool rather than nylon fibers.     

Dynamics of trans-cis photoisomerization of hetarylazo dyes

Dynamics of trans-cis photoisomerization of novel hetarylazo dyes containing hydrogenated quinoline and triazole or tetrazole moieties has been studied by femtosecond laser photolysis with spectrophotometric detection. For all the dyes under study, the absorbance dynamics after photoexcitation in the long-wavelength absorption band (λ_pump = 550 nm) is described by three fast processes with characteristic times of 0.07–0.27, 0.4–1.0, and 3–7 ps. The effect of the solvent and the azo dye structure on the dynamics of transient species has been investigated.     

Supramolecular motifs in s-block metal-bound sulfonated monoazo dyes, part 1: structural class controlled by cation type and modulated by sulfonate aryl ring position

The solid-state structures of 43 Li, Na, K, Rb, Mg, Ca and Ba salts of para- and meta-sulfonated azo dyes have been examined and can be categorised into three structural classes. All form alternating organic and inorganic layers, however, the nature of the coordination network that forms these layers differs from class to class. The class of structure formed was found to be primarily governed by metal type, but can also be influenced by the nature and position of the organic substituents. Thus, for the para-sulfonated azo dyes, Mg compounds form solvent-separated ion-pair solids; Ca, Ba and Li compounds form simple coordination networks based on metal-sulfonate bonding; and Na, K and Rb compounds form more complex, higher dimensional coordination networks. Compounds of meta-sulfonated azo dyes follow a similar pattern, but here, Ca species may also form solvent-separated ion-pair solids. Significantly, this first attempt to classify such dyestuffs using the principles of supramolecular chemistry succeeds not only for the simple dyes used here as model compounds, but also for more complex molecules, similar to modern colourants.     

Azocoupling reactions of enaminocarbonyl derivatives of 1,2,3,4-tetrahydroisoquinoline with diazonium salts

It has been shown that enamino amide and enamino ketone derivatives of 1,2,3,4-tetrahydroisoquinoline react with diazonium salts to form azo compounds. Depending on the enamine structure they can exist just as azo dyes or as azohydrazone tautomers. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1382–1387, September, 2006.     

Azo dyes degradation using TiO2-Pt/graphene oxide and TiO2-Pt/reduced graphene oxide photocatalysts under UV and natural sunlight irradiation

The photocatalytic degradation of azo dyes with different structures (amaranth, sunset yellow and tartrazine) using TiO₂-Pt nanoparticles (TPt), TiO₂-Pt/graphene oxide (TPt-GO) and TiO₂-Pt/reduced graphene oxide (TPt-rGO) composites were investigated in the presence of UV and natural sunlight irradiation. The composites were prepared by a combined chemical-thermal method and characterized by Transmission Electron Microscopy (TEM), X-ray powder diffraction (XRD), Infrared (FTIR) and UV–Vis spectroscopy. The modification of TiO₂-Pt with graphene oxide shifted its optical absorption edge towards the visible region and increased its photocatalytic activity under UV and natural sunlight irradiation. The efficiency of catalysts on azo dyes degradation (in similar conditions) reached high values (above 99%) under sunlight conditions, proving the remarkable photocatalytic activities of obtained composites. TPt-GO nanocomposite exhibited higher photoactivity than TPt or TPt-rGO, demonstrating degradation efficiencies of 99.56% for amaranth, 99.15% for sunset yellow and 96.23% for tartrazine. The dye photodegradation process follows a pseudo-first-order kinetic with respect to the Langmuir-Hinshelwood reaction mechanism. A direct dependence between azo dyes degradation rate and chemical structure of dyes has been observed.     

Crown ether-containing styryl dyes

The method for the synthesis of indoles from nitropyridinium salts has been improved. A method for synthesizing novel derivatives of indoleninium quaternary salts has been developed. The condensation of indoleninium salts with formyl derivatives of crown ethers leading to styryl dyes is described. Photoisomerization and complexing of crown-ether dyes with ions of alkaline and alkaline-earth metals have been studied. The shift of the long-wave absorption maximum has been observed to depend on the size and charge density of the metal cation.For communication 8, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1625–1632, September, 1993.     

Use of titanium dioxide photocatalysis on the remediation of model textile wastewaters containing azo dyes

The photocatalytic degradation of two commercial textile azo dyes, namely C.I Reactive Black 5 and C.I Reactive Red 239, has been studied. TiO(2) P25 Degussa was used as catalyst and photodegradation was carried out in aqueous solution under artificial irradiation with a 125 W mercury vapor lamp. The effects of the amount of TiO(2) used, UV-light irradiation time, pH of the solution under treatment, initial concentration of the azo dye and addition of different concentrations of hydrogen peroxide were investigated. The effect of the simultaneous photodegradation of the two azo dyes was also investigated and we observed that the degradation rates achieved in mono and bi-component systems were identical. The repeatability of photocatalytic activity of the photocatalyst was also tested. After five cycles of TiO(2) reuse the rate of colour lost was still 77% of the initial rate. The degradation was followed monitoring the change of azo dye concentration by UV-Vis spectroscopy. Results show that the use of an efficient photocatalyst and the adequate selection of optimal operational parameters may easily lead to a complete decolorization of the aqueous solutions of both azo dyes.     

Oxazole ring cleavage in the course of the synthesis of heterocyclic azo dyes

The formation of azo dyes by coupling the diazonium salts of aminophenyloxazolopyridines with N,N-di-ethylaniline was shown to be a suitable probe to check the stability of the oxazole ring in the course of their preparation. Depending on experimental conditions, “closed” and “opened” systems could be obtained separately.     

Investigation of interaction strategies between pyrazolone dyes and poly(acrylamide-co-acrylic acid)

The removal of dyes from waste water before their discharge into aquatic ecosystems is of substantial concern. Amongst functional macromolecules, the combination of polymers with dyes is a research field of enormous potential with regard to high-performance materials. The present study investigates interactions strategies between P(AM-co-AA) polymer with pyrazolone azo dyes in water as green solvent. These interactions were confirmed by FTIR spectroscopy, Ultra-visible spectroscopy, EDAX analysis, and FE-SEM analysis. Polymer P(AM-co-AA) has porous structure in which dyes present in the water get absorb hence it is use to remove pyrazolone dyes from water.

     

Extraction-chromatographic determination of sulfonated azo dyes in aqueous solutions

The extraction of sulfonated azo dyes E102, E110, E122, E124, and E129 from aqueous solutions using hydrophilic solvents and their mixtures in the presence of a salting-out agent (ammonium sulphate) has been studied. Some regularities of extraction have been revealed. The composition of the mobile phase has been optimized and a procedure has been proposed for the identification and determination of the dyes in aqueous solutions by thin-layer chromatography in concentrations of 0.1–0.01 μg/L. An office scanner and a personal computer have been used to process the results of the separate determination of the dyes.     

Analysis of electrochemical degradation products of sulphonated azo dyes using high-performance liquid chromatography/tandem mass spectrometry

Electrochemical treatment of wastewaters containing azo dyes in the textile industry is a promising approach for their degradation. The monitoring of the course of the decomposition of azo dyes in wastewaters is essential due to the environmental impact of their degradation products. In this work, aqueous solutions of a simple azo dye with a low molecular weight (C.I. Acid Yellow 9) and more complex commercial dye (C.I. Reactive Black 5) were electrochemically treated in a laboratory-scale electrolytic cell in sodium chloride or ammonium acetate as supporting electrolytes. Ion-pairing reversed-phase high-performance liquid chromatography coupled with negative-ion electrospray ionization mass spectrometry is applied for the identification of electrochemical degradation products. In addition to simple inorganic salts, the formation of aromatic degradation products obtained due to the cleavage of azo bonds and further degradation reactions is shown, as well as chlorination where sodium chloride is the supporting electrolyte. Degradation mechanisms are suggested for the treatment with sodium chloride as the supporting electrolyte.     

Synthesis and spectral properties of new hetarylazo indole dyes

A series of new hetarylazo indole dyes were synthesized by azo coupling of 2-phenyl-, 2-methyl-, and 1-methyl-1-phenyl-1H-indole with diazonium salts derived from 5-methylsulfanyl-1H-1,2,4-triazol-3-amine, 1H-1,2,4-triazol-3-amine, 5-methylisoxazol-3-amine, and 5-amino-1,3,4-thiadiazole-2-thiol. The dyes were characterized by the IR spectra, electronic absorption spectra in the UV and visible regions, and ¹H NMR and mass spectra. The effects of solvent nature, acidity of the medium, temperature, and concentration on the electronic absorption spectra in the visible region and the dependence of the color of the dyes on the nature of heterocyclic fragment were examined. Published in Russian in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 7, pp. 1041–1047. The text was submitted by the authors in English.     

Ionic liquid 1-(3-Trimethoxysilylpropyl)-3-methylimidazolium nitrite as a new reagent for the efficient diazotization of aniline derivatives and in situ synthesis of azo dyes

A new ionic liquid 1-(3-trimethoxysilylpropyl)-3-methylimidazolium nitrite was synthesized. This ionic liquid was used as a convenient nitrosonium source in diazotization of arylamines into their corresponding diazonium salts which were converted into their related azo dyes via the in situ azo-coupling with aniline derivatives or phenolic compounds. The diazotization of anilines in this ionic liquid and subsequent azo-coupling generated the related azo dyes in good to excellent yields at 0?C5 °C in short reaction times via a simple experimental procedure.     

Polymethine dyes based on pyrroloanthrone

Pyrroloanthrone has been used as the starting material in the synthesis of 6-methylthionaphthindolinium salts that were used in turn to obtain polymethine dyes. The dependence of the color of the cyanines on their chemical structure has been analyzed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1413–1420, October, 1990.     

Oxidation of azo dyes with inorganic peroxides in the presence of cationic surfactants

Degradation of Direct Red 23, Rective Red 45, and Orange II azo dyes with hydrogen peroxide and hydroperite in the presence of cationic surfactants alkyldimethylbenzylammonium chloride (Katamin AB) and cetyltrimethylammonium chloride and without them was studied by spectrophotometry. The reactivity of the azo dyes was correlated with their chemical structure.     

Synthesis and characterization of guest-host azo dyes with broad absorption bands

Abstract

Three groups of dyes were synthesized and characterized in order to examine their solubility, absorption spectrum, and order parameter in liquid crystal hosts. Our synthesis method allowed the formation of the diazonium salts and the diazo coupling in ethyl acetate instead of an aqueous medium, permitting the formation of long and neutral azo dyes. In the liquid crystal BDH-E7, they showed order parameters in the range of 0.52 to 0.76. The two dyes with the longest molecular lengths were particularly interesting due to their very broad absorption spectra in the visible region. Each of these two compounds behave as single component black dye guest/host systems, which generally require a mixture of two or three dyes in the liquid crystal host. These dyes were also evaluated for use in polymer dispersed liquid crystal films.     

Poly(organophosphazenes) containing azo dyes

In this paper we describe a method for the functionalization of catenapoly[bis(4-hydroxyphenoxy)-λ⁵-phosphazene] with diazonium salts to form new, deeply-coloured, phosphazene copolymers containing variable amounts of azo dyes attached to the polyphosphazene skeleton. The degree of functionalization in these substrates is regulated in order not to exceed 20% of the sites available in the pristine polyphosphazene and to maintain a high percentage of unreacted, free, hydroxy groups, in the final, coloured copolymers. These species are still very reactive and able to undergo further functionalization reactions.     

A spectral approach to determine location and orientation of azo dyes within surfactant aggregates

The UV–vis absorption properties of azo dyes are known to exhibit a variation with the polarity and acidity of the dye environment. The spectral properties of a series of anionic azo dyes were characterized to further probe the interaction of these dyes with two types of surfactant aggregates: (1) the spherical micelles formed in aqueous solution by alkyltrimethylammonium bromide (C_nTAB) surfactants with n = 10–16 and (2) the unilamellar vesicles spontaneously formed in water from binary mixtures of the oppositely-charged double-tailed surfactants cationic didodecyldimethylammonium bromide (DDAB) and anionic sodium dioctylsulfosuccinate (Aerosol OT or AOT). The observed dye spectra reflect the solvatochromic behavior of the dyes and suggest the location and orientation of the dye within the surfactant aggregates. Deconvolution of the overall spectra into sums of Gaussian curves more readily displays any contributions of tautomeric forms of the azo dyes resulting from intramolecular hydrogen bonding. The rich variation in UV/vis absorption properties of these anionic azo dyes supports their use as sensitive tools to explore the nanostructures of surfactant aggregates.     

Energy structures and electronic-transition wavelengths for trinuclear polymethine dyes

A study has been made on the energy structures and long-wave electronic transitions for linear trinuclear polymethine dyes by the method of additive generating functions. The necessary and sufficient conditions have been established for the occurrence of local levels related to the central nucleus. It is found that the bisvinylene shift is dependent on the structure of the central nucleus in this class of dyes. The relationship fits the available measurements, and it is predicted that there is a positive bridge effect, namely an increase in the bisvinylene shift in trinuclear dyes by comparison with binuclear ones.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 10–21, January–February, 1987.